It is a common practice in the art to recover cotton seeds from the lint which remains after the cotton product itself is separated from the crop. The seeds so recovered are used for the production of cotton seed oil and, in some cases, for planting purposes. In cases where the seed is recovered for planting purposes, care must be taken not to damage the seeds such that germination would be impaired. In the recovery of cotton seed from the lint, there are several different methods which are commonly used.
The older and less frequently used method is known as mechanical delinting. This method involves separating the seed from the lint by using saw delinting and/or brush delinting. In the saw delinting method, the lint is cut from the seeds by means of saws, after which the seeds may be dropped through a flame to remove the residual portion of the lint remaining after the saw delinting step.
Another type of mechanical delinting is known as brush delinting. in this method, a series of brushes are rotated against the inner surface of a perforated drum in which the fuzzy seeds are loaded, whereby Eke lint is removed from the seeds mainly by friction.
A mechanical delinting process which is particularly suitable for recovery of seed from lint for planting purposes is disclosed in U.S. Pat. No. 5,249,335--Jones, which is assigned to the same assignee as the present application.
Another approach to the recovery of seed for. planting purposes involves utilizing chemical methods which include the use of hydrogen chloride gas and sulfuric acid. There are several different approaches which have been employed in the use of these chemicals to delint fuzzy cotton seed.
One of these is known as the concentrated sulfuric acid method. In this method, concentrated sulfuric acid is applied to the fuzzy cotton seed. Almost instantly, the acid reacts with the lint and the lint is removed and hydrolyzed into its components. The seed is then rinsed with water to remove the acid and is dried and further processed with seed processing equipment well known in the art.
There are two major disadvantages with the concentrated sulfuric acid method. One is that the rinse water represents an environmental problem and the other is that the process also removes the oil in the seed coat which shortens the shelf life or the time period in which the seed remains viable.
Another chemical method is known as the anhydrous hydrogen chloride gas method. This method involves injecting HCl gas into a closed reaction chamber which contains a charge of fuzzy seed. The HCl gas reacts with the lint on the seed and the seed is then emptied from the reaction chamber into a buffer. In the buffer, the lint is buffed from the seed by means of rotating screens.
A disadvantage of the anhydrous hydrogen chloride gas method is that any of the seeds which have been cracked or otherwise physically damaged or which have openings of any kind in the shell of the seed will be killed by the entry of the gas into the interior of the seed. Also, the gas is hygroscopic and the system can. therefore be used only in an arid or semi-arid environment where the relative humidity is consistently low.
knother chemical method is known as the dilute sulfuric acid method which was developed to avoid many of the disadvantages of the above discussed chemical methods. In this method, a dilute sulfuric acid solution of approximately 10% by weight of sulfuric acid and approximately 0.05% of surfactant (used as a wetting agent) in water is used to dampen the lint on the fuzzy seed. The dampened fuzzy seed is then dried in rotary driers, which are typically about six feet in diameter and about thirty feet long.
As the temperature of the dampened fuzzy seed is increased in the driers, the water in the solution, which has a lower boiling point than the acid, will begin to evaporate from the seed thereby causing the acid which remains on the seed to become more concentrated. As the acid concentration on the fuzzy seed approaches 100%, the lint is abruptly hydrolyzed by the acid and breaks off from the seed in the form of a dry powder. The powder is removed by the heated air stream used in the drying process.
The dilute sulfuric acid methods in use at the present time differ from each other primarily in the methods which are used to apply the dilute acid solution to the fuzzy seed. In the centrifuge method, the cotton seed is first flooded with dilute acid and then partially dried by centrifuging to produce basically a 10% wet pick-up on the seed. In the foam acid system, a foam generator converts the dilute acid solution to foam which is then applied to the seed. Other methods involve the direct application of the dilute acid solution to the seed.
In the dilute acid process as practiced in the prior art, the dilute acid solution is typically added in large amounts to large bulk quantities of fuzzy seed. This is done by flooding, spraying or the like of the dilute acid solution on large bulk quantities of seed as described above and requires relatively severe agitation of the seed to provide for the distribution of the acid solution throughout the seed bulk with resulting trauma to the seed. In addition, such prior art methods of applying the dilute acid solution to the fuzzy seed typically result in the application of excess acid to the seed. When subjected to the drying and hydrolyzation reaction, this excess acid can further damage the seed.
Present dilute acid systems are large, continuous process systems which are configured for continuous product throughput. Such systems have been found to be advantageous in the recovery of seed for planting in large volume commercial applications where relatively harsh conditions are acceptable and where the seed are graded after recovery depending upon the quality thereof. However, such prior art systems are not suitable for use in the recovery of "breeder seed" in relatively small quantities where, in particular, the seeds are from new varieties and therefore very valuable in the process of increasing from just a few seeds to large scale commercial quantities. In these cases, the new seed varieties which have desirable fiber characteristics may also be more easily damaged because the seed coats may be thinner or otherwise subject to damage or because the new seeds may be more vulnerable to impact, heat or other parameters typically encountered in the recovery process.
Such valuable breeder seeds can thus be subject to damage and even the loss thereof when subjected to the recovery conditions typically present in the large commercial delinters of the prior art as described above. For example, such seed may be easily damaged when subjected to vigorous agitation such as used in large commercial delinters such as those described above. The same applies to the high temperatures typically present in the driers used in the dilute acid method.
In such prior art commercial delinters, the dilute acid saturated fuzzy seed are tumbled within a large continuously rotating drum in which heated air is circulated. The saturated fuzzy seed are continuously introduced into the drum at one end thereof and continuously removed at the other end thereof. Drying and hydrolysis and carried out as a continuous process as the seed are agitated and moved axially within the drum from the input end to the exit end where the delinted seed are removed.
The whole process is thus continuous. That is, the dilute acid saturated fuzzy seed are loaded into the drum at one end and are moved axially within the drum while being agitated or tumbled to carry out drying and hydrolysis. The length of the drum and the other parameters related to the delinting process are selected such that the process is completed as the seed reach the exit end of the rotating drum. Thus, the seed are moved axially as well as radially within the drum.
In addition, the configuration and rotational velocity of the drum is such that the seed are pitched or lofted during rotation of the drum to cause them to impact the internal metal surfaces of the drum, thereby causing trauma to the seed. This trauma causes damage to the seed and reduces its suitability for planting purposes.
Accordingly, there has existed a need for a cotton seed delinting system that can be fabricated with a low capital investment and which meets the following criteria:
(a) The ability to delint seed with thin walled seed coats. Such seed is easily damaged when vigorously agitated as is the case with large commercial delinters. In such large commercial delinters, the seed coats tend to crack and fall off the seed, thereby preventing the ability to maintain high quality seed standards.
(b) The ability to delint seed at low temperatures in order to prevent heat damage to the seed. This is of particular importance when dealing with small increase lots developed at the research stage where supplies of the seed are limited.
(c) The ability to delint seed in small quantities which are in an increase program (a program to increase supply) or which are otherwise in limited supply. It has been found to be almost impossible to delint small amounts of cotton seed in continuous flow systems.
(d) The ability to be easily moved from one location to another to permit delinting on site on small land areas which would not accommodate the construction of a large scale fixed installation.
All of the foregoing criteria should be present without significant adverse impact on the environment.
It is a primary object of the present invention to provide a batch delinting system which meets at least the foregoing criteria.